Frequently the specific depth of collars and/or other features in the wellbore in a casing string needs to be located with an indication at the surface that the collar has been properly located. In the past this function has been approached with a tool delivered on a string that has one or more collets. The collets and the mandrel that backs them up are configured to allow the collets to remain in an unsupported position for downhole tripping. After the desired collar is reached the tool with the collets is further advanced downhole beyond a locating groove in the collar that is of interest. The tool is then picked back up to engage the collar. Doing this traps the collet in the groove and an overpull is applied. The resistance to the overpull is sensed at the surface. The collet is designed to release after a predetermined level of pulling force is reached.
There are several issues with this design. In deep wells with a significant amount of deviation there is a substantial risk of drag of the work string in the surrounding tubular so that the overpull applied could be the force required to dislodge the work string as opposed to a pull on the collets that may not even have landed in the locator groove of the collar in question. This drag effect induced by depth and well deviation is commonly referred to as a “slip/stick effect”. There may be no ascertainable signal at the surface if the slip/stick effect is present. Another problem is the limit of stress that can be applied to the collet heads that are in the locating groove. While the collet structure can be made thicker the problem there is that the material may be limited in the level of stress that can be endured on the trapped collet heads. Another issue is limited space and tool diameter restriction required to actually deliver the tool to the collar in interest. Thus making the parts thicker may not be sufficiently helpful to increase the overall rating toward the desired pulling force required or there may not be the room required to go this route. Another issue with the collet based systems is that upon release there is a slingshot effect as the stored potential energy in the applied pulling force on the work string is suddenly released as the collets become unsupported when a predetermined pulling force is reached.
Accordingly what is needed and is addressed by the present invention is a tool that can handle greater applied forces than the collet based designs and on that can eliminate the slingshot effect. Other desirable features can be a built in delay that allows higher loads to be applied for a defined time period to be sure that the collar is properly located and that the slip/stick forces have been overcome. A rapid re-cocking of the tool after a release for repeated testing is also a feature. The tool can be inverted and properly regulated so as to apply a predetermined downward force on a bottom hole assembly working in conjunction with a heave compensator for offshore drilling applications. These and other features of the present invention will become more apparent to those skilled in the art from a review of the description of the preferred embodiment, the drawings and the claims that determine the scope of the invention, all of which appear below.